Former Florida Gov. Jeb Bush, right, poses for a pictures with supporters after holding a town hall meeting with Puerto Rico's Republican Party in Bayamon in April. Residents of Puerto Rico may be U.S. citizens but they can't vote for president. The parade of presidential hopefuls to the territory speaks to the growing power of Puerto Rican voters on the mainland, almost exclusively Florida, the top destination for those fleeing the island’s 12 percent unemployment rate and nine-year economic slump.

A decade-long recession in Puerto Rico has forced an unprecedented number of the islanders to look for economic opportunities on the mainland, particularly in central Florida.

More than a million Puerto Ricans now live in the Sunshine State, a number that has doubled since 2000 and now equals that of New York.

Like most residents of US territories, Puerto Ricans can’t vote in the general US presidential elections at home, but they can from the mainland, which means that their mass migration to Florida could prove instrumental to the outcome of the 2016 presidential election.

The race in Florida is notoriously tight. In 2012, President Obama barely won the state from Mitt Romney, with 50 percent of the vote, compared to Mr. Romey’s 49.1 percent.

“It’s a potential game changer for the state,” Mark Hugo Lopez, director of Hispanic Research at the Pew Research Center, told The Washington Post.

“It’s the biggest movement of people out of Puerto Rico since the great migration of the 1950s.”

According to the Pew Research Center, a majority of Puerto Ricans, 57 percent, identify as Democrats, though many don’t identify with any party, providing an opportunity for each party to recruit these valuable new voters.

By comparison, 48 percent of Cubans, who have shaped Florida’s electorate historically, identify as Democrats. But Florida’s Cuban population, at 1.4 million in 2014, has grown 65 percent since 2000, a modest increase compared with 110 percent growth in the Puerto Rican population in the same years, according to Pew.

“I do think Puerto Ricans can change the political landscape,” said Cristóbal Alex, president of the Democratic-backed Latino Victory Project, to the Post.

“I think you are going to see a hyper-focus in Florida, the likes of which we have never seen,” Mr. Alex said.

Social services and political organizations in the state are working to register Puerto Rican newcomers to vote.

On a recent weekend, reports National Public Radio, the nonprofit Mi Familia Vota, a national organization based in Arizona that works to engage Latinos in the political process, co-sponsored a social services fair for newly arrived Puerto Ricans. Families enrolled in health care and job opportunities there, and registered to vote.

Meanwhile, conservative organizations like the Texas-based LIBRE Initiative are focusing on educating newcomers about economic policies, knocking on doors in high Latino-population areas to offer English and financial literacy classes, and to promote the virtues of limited government.

"We think that a limited government equals more opportunities for people to start a business to rise up and have success in the country," explained David Velazquez, deputy Florida director for LIBRE to NPR as he knocked on doors in the overwhelmingly Puerto Rican neighborhood of Buenaventura Lakes in Osceola County.